Mastering Biology - Chapter 9: Cell Communication

Thyroid hormones bind to _____ receptors.

intracellular

To what does the term "ligand" refer in cell biology?

any small molecule that can bind in a specific manner to a larger one

The toxin of Vibrio cholerae causes profuse diarrhea because it _____.

modifies a G protein involved in regulating salt and water secretion

In addition to testing shmoo formation in the two mutant strains of yeast, the scientists also tested shmoo formation in wild-type yeast.

to show normal shmoo formation under the experimental conditions

Which of these is a signal molecule?

A

Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine. Complete the flowchart showing the process of histamine signal transduction from the H1 receptor.

1. Enzyme cleaves PIP2, forming DAG and IP3. 2. IP3 binds to a ligand-gated ion channel in the ER membrane. 3. Calcium ion flow through the ligand-gated ion channel. 4. Calcium ion concentration increases in the cytosol. 5. Calcium ions activate a protein, leading to a cellular response.

Put the steps of the process of signal transduction in the order they occur:1. A conformational change in the signal-receptor complex activates an enzyme.2. Protein kinases are activated.3. A signal molecule binds to a receptor.4. Target proteins are phosphorylated.5. Second messenger molecules are released.

3, 1, 5, 2, 4

Which of these is a G-protein-linked receptor?

A

Which of the following sequences is correct?

All of the choices are correct.

Which of these is a receptor molecule?

B

The binding of signal molecules to _____ results in the phosphorylation of tyrosines.

C

Which of these is a receptor tyrosine kinase?

C

Which of these is an ion-channel receptor?

D

Which of these receptor molecules would allow Na+ to flow into the cell?

D

_____ is a signal molecule that binds to an intracellular receptor

D

Which of these receptors is NOT a membrane receptor?

E

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

Estrogen binds to specific receptors inside many kinds of cells, each with different responses.

What hypothesis was being tested with the Δformin strain?

Formin is required for the signal transduction pathway leading to shmoo formation.

A model helps scientists form testable hypotheses. What hypothesis was being tested with the ΔFus3 strain?

Fus3 is required for the signal transduction pathway leading to shmoo formation.

Which of the following is a correct association?

GTPase activity and hydrolysis of GTP to GDP

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

Glycogen breakdown was observed only when epinephrine was administered to intact cells.

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following, if found in cells or organisms as they age, would provide evidence that this is related to cell signaling?

Growth factor ligands do not bind as efficiently to receptors.

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

Ligand-gated ion channel

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because _____.

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because _____.

Why is apoptosis potentially threatening to the healthy "neighbors" of a dying cell?

Lysosomal enzymes exiting the dying cell would damage surrounding cells.

A steroid hormone, like estrogen, passes through the plasma membrane and binds to an intracellular protein as shown in the diagram below. This activates a signal-transduction pathway which results in an increased production of a specific protein.Which of the following statements would explain what would occur as a result of the signal pathway represented by the diagram?

Messenger RNA (m-RNA) levels would increase in order to be translated into the protein required by the cell.

What do you predict would happen if the yeast had a mutation that prevented the G protein from binding GTP?

No shmoo would form in response to mating factor.

Which of the following statements is true of signal molecules?

Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.

Protein phosphorylation is commonly involved with all of the following except

Protein phosphorylation is commonly involved with all of the following except

Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of the process. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response.

Reception: G protein-coupled receptor, receptor tyrosine kinase, signaling molecule Transduction: phosphorylation cascade, second messenger, adenlyl cyclase, IP3, Ca2+, cAMP. Response: protein synthesis

Which of the following describes the events of apoptosis?

The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells.

The histamine H1 receptor is one of several existing histamine G protein-coupled receptors. Depending on many factors, including the type of receptor, histamine can trigger a variety of responses, including vasodilation, smooth muscle contraction, stimulation of gastric secretion, cardiac stimulation, and increased vascular permeability (causing runny nose and watery eyes).

The enzyme that is activated by the G protein associated with the receptor. The types of relay molecules within the cell. The type of second messengers involved in the signal transduction pathway. The cell type in which the histamine receptor is located.

Why has C. elegans proven to be a useful model for understanding apoptosis?

The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.

Fus3 kinase and formin proteins are generally distributed evenly throughout a yeast cell. Based on the model in the diagram, why does the shmoo projection emerge on the same side of the cell that bound the mating factor?

The only formin molecules that get phosphorylated and thus activated are those near the G protein-coupled receptor that binds mating factor.

Why can a signaling molecule cause different responses in different cells?

The transduction process is unique to each cell type; to respond to a signal, different cells require only a similar membrane receptor.

When designing an experiment, scientists make predictions about what results will occur if their hypothesis is correct. One of their hypotheses was that Fus3 kinase is required for the signal transduction pathway leading to shmoo formation. If this hypothesis is correct, what result should be observed in the ΔFus3 strain?

The ΔFus3 strain should not form shmoos, and the cells should not have a red zone in their walls.

One of their hypotheses was that formin is required for the signal transduction pathway leading to shmoo formation. If this hypothesis is correct, what result should be observed in the Δformin strain?

The Δformin strain should not form shmoos, and the cells should not have a red zone in their walls.

Which of the following is true during a typical cAMP-type signal transduction event?

Which of the following is true during a typical cAMP-type signal transduction event? Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

Which of the following is true of steroid receptors?

Which of the following is true of steroid receptors?

The micrographs shown below were taken of wild-type, ΔFus3, and Δformin cells after they were stained green, exposed to mating factor, and then stained red. For each micrograph, drag the labels to answer the questions. Labels may be used once, more than once, or not at all

Wild type: red and green, asymmetrical, yes, yes, yes. ΔFus3: yellow, symmetrical, no, yes, yes. Δformin: yellow, symmetrical, no, yes, yes.

A drug designed to inhibit the response of cells to testosterone would most likely result in _____.

a decrease in transcriptional activity of certain genes

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result?

a form of cancer in which there is insufficient apoptosis

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?

a lipid-soluble signal

Protein kinase is an enzyme that _____.

activates or inactivates other proteins by adding a phosphate group to them

Protein phosphorylation is commonly involved with all of the following EXCEPT _____.

activation of G protein-coupled receptors

A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.Where would you expect to find the carboxyl end?

at the cytosol surface

A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.The coupled G protein most likely interacts with this receptor _____.

at the loop between H5 and H6

Testosterone functions inside a cell by _____.

binding with a receptor protein that enters the nucleus and activates specific genes

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of _____.

cAMP

Which of the following are among the most common second messengers?

calcium ion and cAMP

Transcription factors _____.

control gene expression

What is the function of tyrosine-kinase receptors?

enzymatic phosphorylation of tyrosine in the receptor protein

Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor?

estrogen

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must _____.

have receptors that recognize and bind the hormone molecule

GTPase activity is important in the regulation of signal transduction because it _____.

hydrolyzes GTP to GDP, thus shutting down the pathway

Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. HER2 is sometimes excessive in cancer cells. This information can now be utilized in breast cancer treatment if which of the following is true?

if the patient's cancer cells have excessive levels of HER2

In signal transduction, phosphatases _____.

inactivate protein kinases and turn off the signal transduction

Scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testes. For this to happen there must be direct communication between the extracellular matrix and the developing cells. Which kind of transmembrane protein would most likely be involved in this kind of induction?

integrins

Which of the following is characteristic of a steroid hormone action?

internal receptor binding

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because

intracellular receptors are present only in target cells.

A G-protein receptor with GTP bound to it _____.

is in its active state

A signal molecule is also known as a(n) _____.

ligand

Apoptosis involves all but which of the following?

lysis of the cell

In the figure, the dots in the space between the two structures represent which of the following?

neurotransmitters

Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?

paracrine signaling

Adenylyl cyclase has the opposite effect of which of the following?

phosphodiesterase

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?

phospholipase C

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

receptor tyrosine kinase activity

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

receptor tyrosine kinases

In general, a signal transmitted via phosphorylation of a series of proteins _____.

results in a conformational change to each protein

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?

serine and threonine

A signal transduction pathway is initiated when a _____ binds to a receptor.

signal molecule

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

signal molecule

A(n) _____ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off.

steroid

The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is not a problem for steroids because _____.

steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane

Which of the following types of signaling is represented in the figure?

synaptic

Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting _____.

the hydrolysis of cGMP to GMP

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound _____.

to block G protein activity in liver cells

Dioxin, produced as a by-product of various industrial chemical processes, is suspected of contributing to the development of cancer and birth defects in animals and humans. It apparently acts by entering cells by simple diffusion and binding to proteins in the cytoplasm, then altering the pattern of gene expression. Which of the following are likely to be the cytoplasmic proteins to which dioxin binds?

transcription factors

Which of these is the second of the three stages of cell signaling?

transduction